Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas
High-resolution charge-exchange recombination spectroscopic measurements of B[superscript 5+] ions have enabled the first spatially resolved calculations of the radial electric field (E[subscript r]) in the Alcator C-Mod pedestal region [ E. S. Marmar, Fusion Sci. Technol. 51, 261 (2006) ]. These ob...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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American Institute of Physics
2010
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| Online Access: | http://hdl.handle.net/1721.1/55957 https://orcid.org/0000-0001-8319-5971 https://orcid.org/0000-0002-9001-5606 https://orcid.org/0000-0002-7841-9261 https://orcid.org/0000-0002-4438-729X https://orcid.org/0000-0002-0349-1736 |
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| author | Lipschultz, Bruce McDermott, R. M. Catto, Peter J. Granetz, Robert S. Greenwald, Martin J. Labombard, Brian Marr, K. Rice, John E. Alcator C-Mod Team Reinke, Matthew Logan Hutchinson, Ian Horner Hughes Jr, Jerry Hubbard, Amanda E Whyte, Dennis G |
| author2 | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Lipschultz, Bruce McDermott, R. M. Catto, Peter J. Granetz, Robert S. Greenwald, Martin J. Labombard, Brian Marr, K. Rice, John E. Alcator C-Mod Team Reinke, Matthew Logan Hutchinson, Ian Horner Hughes Jr, Jerry Hubbard, Amanda E Whyte, Dennis G |
| author_sort | Lipschultz, Bruce |
| collection | MIT |
| description | High-resolution charge-exchange recombination spectroscopic measurements of B[superscript 5+] ions have enabled the first spatially resolved calculations of the radial electric field (E[subscript r]) in the Alcator C-Mod pedestal region [ E. S. Marmar, Fusion Sci. Technol. 51, 261 (2006) ]. These observations offer new challenges for theory and simulation and provide for important comparisons with other devices. Qualitatively, the field structure observed on C-Mod is similar to that on other tokamaks. However, the narrow high-confinement mode (H-mode) E[subscript r] well widths (5 mm) observed on C-Mod suggest a scaling with machine size, while the observed depths (up to 300 kV/m) are unprecedented. Due to the strong ion-electron thermal coupling in the C-Mod pedestal, it is possible to infer information about the main ion population in this region. The results indicate that in H-mode the main ion pressure gradient is the dominant contributor to the Er well and that the main ions have significant edge flow. C-Mod H-mode data show a clear correlation between deeper E[subscript r] wells, higher confinement plasmas, and higher electron temperature pedestal heights. However, improved L-mode (I-mode) plasmas exhibit energy confinement equivalent to that observed in similar H-mode discharges, but with significantly shallower E[subscript r] wells. I-mode plasmas are characterized by H-mode-like energy barriers, but with L-mode-like particle barriers. The decoupling of energy and particle barrier formation makes the I-mode an interesting regime for fusion research and provides for a low collisionality pedestal without edge localized modes. |
| first_indexed | 2024-09-23T08:29:45Z |
| format | Article |
| id | mit-1721.1/55957 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:29:45Z |
| publishDate | 2010 |
| publisher | American Institute of Physics |
| record_format | dspace |
| spelling | mit-1721.1/559572023-02-26T02:09:22Z Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas Lipschultz, Bruce McDermott, R. M. Catto, Peter J. Granetz, Robert S. Greenwald, Martin J. Labombard, Brian Marr, K. Rice, John E. Alcator C-Mod Team Reinke, Matthew Logan Hutchinson, Ian Horner Hughes Jr, Jerry Hubbard, Amanda E Whyte, Dennis G Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Massachusetts Institute of Technology. Plasma Science and Fusion Center Hutchinson, Ian H. Hutchinson, Ian H. Lipschultz, Bruce McDermott, R. M. Hughes, Jerry W. Catto, Peter J. Hubbard, Amanda E. Granetz, Robert S. Greenwald, Martin J. Labombard, Brian Marr, K. Rice, John E. Whyte, Dennis G. Alcator C-Mod Team Reinke, Matthew Logan High-resolution charge-exchange recombination spectroscopic measurements of B[superscript 5+] ions have enabled the first spatially resolved calculations of the radial electric field (E[subscript r]) in the Alcator C-Mod pedestal region [ E. S. Marmar, Fusion Sci. Technol. 51, 261 (2006) ]. These observations offer new challenges for theory and simulation and provide for important comparisons with other devices. Qualitatively, the field structure observed on C-Mod is similar to that on other tokamaks. However, the narrow high-confinement mode (H-mode) E[subscript r] well widths (5 mm) observed on C-Mod suggest a scaling with machine size, while the observed depths (up to 300 kV/m) are unprecedented. Due to the strong ion-electron thermal coupling in the C-Mod pedestal, it is possible to infer information about the main ion population in this region. The results indicate that in H-mode the main ion pressure gradient is the dominant contributor to the Er well and that the main ions have significant edge flow. C-Mod H-mode data show a clear correlation between deeper E[subscript r] wells, higher confinement plasmas, and higher electron temperature pedestal heights. However, improved L-mode (I-mode) plasmas exhibit energy confinement equivalent to that observed in similar H-mode discharges, but with significantly shallower E[subscript r] wells. I-mode plasmas are characterized by H-mode-like energy barriers, but with L-mode-like particle barriers. The decoupling of energy and particle barrier formation makes the I-mode an interesting regime for fusion research and provides for a low collisionality pedestal without edge localized modes. United States Department of Energy (Cooperative Agreement No. DE-FC02-99ER54512) 2010-06-22T19:07:10Z 2010-06-22T19:07:10Z 2009-03 2008-12 Article http://purl.org/eprint/type/SubmittedJournalArticle 1070-664X 1089-7674 http://hdl.handle.net/1721.1/55957 McDermott, R. M. et al. “Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod plasmas.” Physics of Plasmas 16.5 (2009): 056103-12. ©2009 American Institute of Physics. https://orcid.org/0000-0001-8319-5971 https://orcid.org/0000-0002-9001-5606 https://orcid.org/0000-0002-7841-9261 https://orcid.org/0000-0002-4438-729X https://orcid.org/0000-0002-0349-1736 en_US http://dx.doi.org/10.1063/1.3080721 Physics of Plasmas Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Institute of Physics Assistant to Ian Hutchinson |
| spellingShingle | Lipschultz, Bruce McDermott, R. M. Catto, Peter J. Granetz, Robert S. Greenwald, Martin J. Labombard, Brian Marr, K. Rice, John E. Alcator C-Mod Team Reinke, Matthew Logan Hutchinson, Ian Horner Hughes Jr, Jerry Hubbard, Amanda E Whyte, Dennis G Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas |
| title | Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas |
| title_full | Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas |
| title_fullStr | Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas |
| title_full_unstemmed | Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas |
| title_short | Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas |
| title_sort | edge radial electric field structure and its connections to h mode confinement in alcator c mod plasmas |
| url | http://hdl.handle.net/1721.1/55957 https://orcid.org/0000-0001-8319-5971 https://orcid.org/0000-0002-9001-5606 https://orcid.org/0000-0002-7841-9261 https://orcid.org/0000-0002-4438-729X https://orcid.org/0000-0002-0349-1736 |
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